Phaeochromocytoma is associated with dysglycaemia, impaired fasting glucose and reduced insulin sensitivity with a prevalence of secondary diabetes occurring in 21-37% of cases. Glucose intolerance is mainly attributed to high circulating levels of catecholamines, causing a hypermetabolic state, which compromises the early phase of insulin secretion and impairs glucose uptake in peripheral tissues. Secondary diabetes from catecholamine excess improves substantially post-surgery, with an up to 80% remission rate. Here, we present a case outlining improved glycaemic control and insulin sensitivity following surgical resection of a phaeochromocytoma in a 65-year-old female with long-standing type 2 diabetes mellitus on basal-bolus insulin with previous total daily dose of 160 units, who was able to discontinue regular insulin administration post-operatively and able to lose a significant amount of weight.
The patient initially presented with abdominal sepsis and symptoms of catecholamine excess with intermittent palpitations and nausea. An abdominal CT scan identified a smooth homogenous 27mm x 25mm nodule in the right adrenal (80 Hounsfield units). Plasma metanephrine levels were markedly elevated: normetanephrine 9458 pmol/L (RR <1080 pmol/L), metanephrine 1873 pmol/L (RR <447 pmol/L), and 3-methoxytyramine at 313 pmol/L (RR <100 pmol/L). Perioperative uptitration of alpha-blockade was complicated by significant postural hypotension and dizziness, but she was able to proceed to laparoscopic adrenalectomy. Immediately following surgery, she was able to discontinue all insulin therapy. Her glycaemic control was maintained with dietary adjustments and gliclazide 60mg modified release daily. Her HbA1c level was 7.7% prior to surgery and improved to 7.2% in the month following surgery. She has subsequently required supplemental NovoRapid doses with meals at substantially reduced doses.
This case highlights the potential impact of phaeochromocytoma on glucose metabolism and the substantial metabolic benefits achievable with treatment. Normalisation of catecholamine levels following tumour resection likely contributed to the observed improvements in weight and insulin requirements.